Compositions and methods for cleaning vapor compression systems

ABSTRACT

Disclosed are azeotrope-like compositions comprising HFC-134a and at least one of HFC-245fa, HFC-365, and HFC-43-10 and methods for using the same to remove contaminants from a vapor compression system.

FIELD OF INVENTION

The present invention relates to non-azeotrope, azeotrope, andazeotrope-like compositions. More specifically, this invention relatesnon-azeotrope, azeotrope, and azeotrope-like mixtures ofhydrofluorocarbons and methods of using the same for removingcontaminants from vapor compression systems.

BACKGROUND OF THE INVENTION

There exists a need to remove contaminants from vapor compressionsystems and their ancillary components when these systems aremanufactured and serviced. As used herein, the term “contaminants”refers to processing fluids, lubricants, particulates, sludge, and/orother materials that are used in the manufacture of these systems orgenerated during their use. In general, these contaminants comprisecompounds such as alkylbenzenes, mineral oils, esters,polyalkyleneglycols, polyvinylethers and other compounds that are madeprimarily of carbon, hydrogen and oxygen.

Vapor compression systems are used in a wide variety of applicationssuch as heating and refrigeration. By compressing and expanding a heattransfer agent, such as a refrigerant, these systems are capable ofabsorbing and releasing heat according to the needs of a particularapplication. Common components of a vapor compression system include:vapor or gas compressors; liquid-cooled pumps; heat transfer equipmentsuch as gas coolers, intercoolers, aftercoolers, heat exchangers, andeconomizers; vapor condensers such as reciprocating piston compressors,rotating screw compressors, centrifugal compressors, and scrollexpanders; control valves and pressure-drop throttling devices such ascapillaries; refrigerant-mixture separating chambers; steam-mixingchambers; connecting piping; and the like. These components aretypically fabricated from copper, brass, steel, and the like, and haveconventional gasket materials.

Many components of a vapor compression system require lubrication toreduce friction caused by their relative physical contact and movements.These lubricants, which are compounds primarily composed of carbon,hydrogen, and oxygen, operate by coating the surfaces of component thatare subjected to friction. Lubricants of a vapor compression system aretypically mixed with the heat transfer agent which carries and dispersesthe lubricant throughout the system. However, during certain processesor procedures, it is desirable to remove these lubricants from thecomponent surfaces, particularly during service operations. Such a needarises, for example, during the retrofitting of a chlorofluorocarbon(CFC) or hydrochlorofluorocarbon (HCFC) refrigerant-based system to ahydrofluorocarbon (HFC)-based system. There is also a need to removeprocessing lubricants during the manufacturing of a system. Failure toremove these types of contaminants from the system may lead to decreasedefficiency or even to the failure of one or more components.

In addition, a vapor compression system may require cleaning after acatastrophic event, such as a compressor blowout. This type of event cancreate contaminants, such as acids, sludge, and particulates, within thesealed system. Failure to remove these types of contaminants from thesystem may also lead to decreased efficiency or failure of one or morecomponents.

The aforementioned contaminants can typically be removed by flushing thevapor compression system with a flushing agent in which the contaminantsare soluble or miscible. Generally, such flushing agents contain one ormore cleaning agents (for example, solvents for various types ofhydrocarbons) and a propellant that carries the cleaning agent throughthe vapor compression system. In some cases, the cleaning agent may alsoserve as the propellant. Until recently, chlorofluorocarbons (CFC's)such as tricholormethane (R-11) and dichlorofluoroethane (R-141) wereused as flushing agents for such systems. Although effective, CFC's arenow considered environmentally unacceptable because of theircontribution to the depletion of the stratospheric ozone layer. As theuse of CFC's is reduced and ultimately phased out, new flushing agentsare needed that not only perform well, but also pose no danger to theozone layer.

Many environmentally acceptable flushing compositions and methods havebeen proposed, but their use has met with limited success. For example,terpenes and low viscosity esters are known solvents of several types oflubricants commonly used in vapor compression systems, such aspolyalkylene glycols, polyol esters, polyvinyl ethers, and the like.However, many of these solvents have a boiling point above 100° C. andare difficult to remove from system components once they have beenintroduced during cleaning. Conventional techniques for removing thesehigh boiling solvents prolongs the flushing operation which iseconomically disadvantageous. In addition, solvent remnants can have adeleterious effect on the performance of the vapor compression system.

One method that has been proposed to deliver a flushing compositionthrough a vapor compression system involves the use of compressednitrogen as the propellant. However, this method of delivery isdifficult and uncertain because the amount of pressure applied by thecompressed nitrogen varies. The use of pressurized nitrogen as apropellant is also expensive. As an alternative to compressed nitrogen,compressed air may be used. However, the use of compressed air bringsthe disadvantage that it often contains an unacceptably high amount ofmoisture. Once introduced, this moisture can be difficult to remove fromthe vapor compression system.

Therefore, Applicants have recognized a need for methods, systems, andcompositions that are environmentally-acceptable and which are capableof effectively and efficiently removing contaminants from vaporcompression systems.

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

Certain embodiments of the present invention meet the aforementionedneeds, among others, by providing novel non-azeotrope, azeotrope, andazeotrope-like compositions comprising HFC-mixtures of1,1,1,2-tetrafluoroethane (HFC-134a) and one or more of1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,3,3-pentafluorobutane(HFC-365), and 1,1,1,2,2,3,4,5,5,5-decafluoropentane (HFC-43-10).Applicants have surprisingly discovered that when an effective amount ofHFC-134a is combined with HFC-365, an azeotrope is formed, and whencombined with HFC-245fa, HFC 43-10, or some combination of HFC-245fa,HFC-365, and HFC 43-10, an azeotrope-like composition is formed.Economical and efficient methods for using such compositions to removecontaminants from vapor compression systems in an environmentallyacceptable manner are also provided.

The term “effective amount”, as used herein, refers to the amount ofHFC-134a, that when combined with one or more of the otheraforementioned components, results in the formation of an azeotrope orazeotrope-like composition.

The term “azeotrope-like”, as used herein, refers to a combination oftwo or more compounds that behave substantially like a single compoundin so far as the vapor in substantial equilibrium with the liquid hassubstantially the same concentration of components present in theliquid. The term “azeotrope-like” is intended to refer to both trueazeotrope compositions and to compositions which are not strictlyazeotropic, but in which the concentration of components in the vaporphase of the composition are so close to the concentration of componentsin the equilibrium liquid phase of the composition as to make separationof the components by ordinary distillation not practically possible. Inessence, the admixture distills without substantially changing itscomposition. This is to be contrasted with non-azeotrope (or “zeotrope”)compositions wherein the liquid composition changes to a substantialdegree during boiling or evaporation.

Azeotropes-like compositions according to the present invention includeabsolute azeotropes (compositions in which azeotropic conditions aresatisfied over all values of temperature (up to the critical stage)) orlimited azeotropes (compositions in which azeotropic conditions aresatisfied only in a certain temperature range). Azeotropes-likecompositions according to the present invention also includehomoazeotropes, wherein the composition exists in a single liquid phase,or heteroazeotropes, wherein the composition exists as two or moreliquid phases. Moreover, azeotrope-like compositions according to thepresent invention can be binary, ternary, quaternary, or quinaryazeotropes depending on whether the composition is composed of 2, 3, 4,or 5 compounds, respectively.

The compounds HFC-245fa, HFC-365, and HFC-43-10 can be used as flushingagents. However, when any of these compounds are used in a flushingapparatus such as a flushing gun, or the like, a propellant may also berequired. Applicants have discovered that HFC-134a can serve as such apropellant. Moreover, as stated above, applicants have discovered thatcertain azeotrope-like compositions are formed by mixing an effectiveamount of HFC-134a with HFC-245fa, HFC-365, HFC 43-10, or somecombination thereof. The azeotrope-like nature of these compositions isuseful when the composition is utilized as a flushing agent, as a heattransfer agent, as a blowing agent for foams, or as an aerosols becauseit allows for uniform condensation and vaporization to occur at a singletemperature. For example, in closed-loop systems such as flushingmachines, an azeotrope-like flushing composition can be recycled becauseof its constant composition ratio in both liquid and vapor states.However, it is understood that azeotrope-like compositions according tothe present invention may also be used in open-loop systems, such asflush guns, although non-azeotrope compositions are preferred.

Applicants have discovered that the preferred azeotrope-likecompositions of the present invention have a number of attributes orproperties that render them particularly effective as flushing agentsfor cleaning vapor compression systems. Many contaminants, includinglubricants, that are commonly found in vapor compression systems areadequately miscible or soluble in the preferred azeotrope-likecompositions of the present invention. The term “adequately miscible”,as used herein, refers to the azeotrope-like composition's ability tointeract with a contaminant to form a solution, emulsion, suspension, ormixture under normal cleaning conditions in such a way that thecontaminant can be effectively removed from the surface needing to becleaned. Examples of such lubricants include, but are not limited to,mineral oils, alkylbenzenes, polyvinylethers, polyalkylene glycols, andpolyol ester oils.

One advantage of the preferred azeotrope-like compositions according tothe present invention is that it is possible to substantially removethese compositions from the treated surface, preferably with relativelylittle effort or complication. For example, the preferred azeotrope-likecompositions evaporate readily using conventional techniques known inthe art such as flushing the system with an inert gas, pulling a vacuumon the system, and/or heating the system. Factors that affectevaporation include vapor pressure, the amount of heat that is applied,the heat conductivity of the liquid, the specific heat of the liquid,the latent heat of vaporization, surface tension, molecular weight, therate at which the vapor is removed. The most appropriate method forremoving the flushing agent for any given application is dependent uponthe characteristics of the application involved and one skilled in theart could readily determine which method would be the most appropriatefor each such application.

One advantage of the present compositions is that each of HFC-245fa,HFC-134a, and HFC-43-10 are nonflammable as defined by ASTME681-94, andtherefore azeotrope-like compositions made from mixtures of thesematerials are also non-flammable. Additionally, other azeotrope-likecomposition according to the present invention, such as certainazeotrope-like mixtures of HFC-365 and HFC134a, may also benon-flammable. Generally, non-flammable mixtures of the presentinvention are preferred because they are less dangerous and thereforeeasier to handle. How, it is understood that mixtures according to thepresent invention may also be flammable, and that in certainapplication, the flammability of these mixtures may be advantageous.

The preferred azeotrope-like compositions of the present invention aregenerally compatible with the materials of vapor compression systems,including metals and sealants.

The preferred azeotrope-like compositions of the present invention areenvironmentally acceptable and do not to contribute to the depletion ofthe earth's stratospheric ozone layer.

Data is presented that demonstrates the existence of binaryazeotrope-like compositions. Non-flammable, substantially constantboiling compositions can also be formed using ternary compositions thatcomprise HFC-134a and two of the other components. However, it should beunderstood that the present invention also provides compositions thatmay also include additional components so as to form new azeotrope-likecompositions. Any such compositions are considered to be within thescope of the present invention provided that the compositions areessentially azeotrope-like and contain all of the essential componentsdescribed herein.

Preferred azeotrope-like compositions of the present invention include:suitable mixtures of HFC-245fa and HFC-134a having from about 1 to about99 weight percent HFC-134a and from about 99 to about 1 weight percentHFC-245fa; suitable mixtures of HFC-134a and HFC-365 having from about60 to about 99 weight percent HFC-134a and from about 1 to about 40weight percent HFC-365; and suitable mixtures of HFC-134a and HFC-43-10having from about 45 to about 99 weight percent HFC-134a and from about1 to about 55 weight percent HFC43-10.

The preferred ratio of components for these preferred azeotrope-likecompositions would depend on many factors, such as material availabilityand cost, the particular equipment to be cleaned, and the composition ofthe contaminants. In view of the teaching contained herein, one skilledin the art could readily select the ratio of components for a specificapplication.

Compositions according to the present invention, including the preferredazeotrope-like compositions, may include one or more components, such asadditives, which may not form new azeotrope-like compositions. Knownadditives may be used in the present compositions in order to tailor thecomposition for a particular use. Inhibitors may also be added to thepresent compositions to inhibit decomposition, react with undesirabledecomposition products, and/or prevent the corrosion of metal surfaces.Typically, up to about 2 percent of an inhibitor based on the totalweight of the azeotrope-like composition may be used.

EXAMPLES

The following examples are illustrative of the practice of the presentinvention:

Example 1

Eighteen grams of HFC-134a were added to an ebulliometer at atmosphericpressure. It was determined that the compound boiled at about −25° C.HFC-245fa was added to the ebulliometer in increments until there was7.04 weight percent (wt. %) of HFC-245fa. Surprisingly, the boilingpoint remained at about −25° C. to about −26° C., indicating that anazeotrope-like composition had formed.

Example 2

A composition comprising 93 wt. % HFC-134a and 7 wt. % HFC-245fa wasproduced and then transferred into a cylinder having a dip tube. To testthe cleaning efficacy of this azeotrope-like composition, a flushingapparatus was assembled that included a cylinder to hold an initialcharge of the azeotrope-like composition, a vaporizing expansion device,an oil separator, and a compressor. An article representing a typicalvapor compression component, such as a condenser, was weighed and thensoiled by depositing approximately 15 grams of polyalkylene glycol (PAG)oil onto its interior surface. The article was then attached to the dipleg of the cylinder containing the azeotrope-like composition so that itcould be cleaned.

The azeotrope-like composition, while in liquid phase, was transferredfrom the cylinder and through the article. As it passed through thearticle, it contacted the soiled surface. As a result of this contact,the PAG oil was dissolved by the azeotrope-like composition, therebyremoving it from the surface of the article. As the azeotrope-likecomposition and dissolved oil exited the article, they passed throughthe expansion device causing the liquid to evaporate. The resultingvapor was passed through an oil separator that removed the oil from theazeotrope-like composition. The azeotrope-like composition was thentransferred to a compressor were it was transformed back to a liquidphase. The liquid azeotrope-like composition was then recycled throughthe article to further clean the article's surface.

After the azeotrope-like composition had circulated through the articlefor 45 minutes, it was found that substantially all of the PAG oil wasremoved from the article. The apparatus was turned off and the articlewas weighed and found to be approximately at its original weight. It wasfound that none of the azeotrope-like composition remained in thearticle.

Example 3

This example illustrates the formation of an azeotrope-like compositionaccording to the present invention and the cleaning efficacy of thatcomposition. For this example, a mixture of 10 wt. % of HFC-134a and 90wt. % of HFC-245fa was formulated and utilized.

The procedure specified in Example 1 was followed to prepare thecomposition, except that a mixture of 10 wt. % of HFC-134a and 90 wt. %of HFC-245fa was formed. Surprisingly, this composition also exhibitedazeotrope-like characteristics.

The cleaning efficacy of this composition was tested using the sameprocedure specified in Example 1. After this azeotrope-like compositionhad circulated through the article for 45 minutes, it was found that thesubstantially all of the PAG oil was removed from the article. Theapparatus was turned off and the article was weighted and found to beapproximately at its original weight. Thus, none of the azeotrope-likecomposition or PAG oil remained in the article.

Example 4

This example illustrates the cleaning efficacy of an azeotrope-likecomposition according to this invention when a flush gun apparatus isutilized. For this example, two pounds of a mixture of 20 wt. % ofHFC-134a and 80 wt. % of HFC-245fa were formulated and then charged intoa flush gun.

The interior of an air conditioning condenser was soiled with 15 gramsof PAG oil. The condenser is arranged so that the azeotrope-likecomposition can flow through it. The outlet of the condenser isconnected to an evacuated recovery cylinder via a high pressurerefrigeration hose. The recovery cylinder is cooled by dry ice. Theinlet of the condenser is attached to the nozzle of the flush gun by asecure fitting and valve.

The valve was opened to allow the azeotrope-like composition to flowfrom the flush gun through the condenser and ultimately into therecovery cylinder. As the azeotrope-like composition passed through thecondenser, it contacted the condenser's soiled surface. As a result ofthis contact, the PAG oil was dissolved by the azeotrope-likecomposition, thereby removing it from the surface of the condenser. Ifrequired, any excess HFC-245fa that became trapped in the condenser wasremoved by dry nitrogen or by passing pure HFC-134a through thecondenser.

After less than 45 minutes, the flushing procedure was stopped. It wasfound that the substantially all of the PAG oil was removed from thecondenser. It was also found that the condenser was substantially freeof the azeotrope-like composition.

Example 5

This example illustrates the cleaning efficacy of an azeotrope-likecomposition according to this invention when a flush gun apparatus isutilized. For this example, a mixture of 20 wt. % of HFC-134a, 30 wt. %of HFC-365, and 50 wt. % of HFC-245fa was formulated and utilized.

Two pounds of a mixture of 20 wt. % of HFC-134a, 30 wt. % of HFC-365,and 50 wt. % of HFC-245fa was charged into a flush gun. The cleaningefficacy of this composition was tested using the same procedurespecified in Example 3.

After less than 45 minutes, the flushing procedure was stopped. It wasfound that the substantially all of the PAG oil was removed from thecondenser. It was also found that the condenser was substantially freeof the azeotrope-like composition.

Example 6

Approximately 18.97 grams of HFC-134a was added to an ebulliometerequipped with a vacuum jacket having a condenser on top and a quartzthermometer. HCF-365mfc is added in small increments. Temperaturedepression was observed when the HFC-365mfc is added, indicating aminimum boiling azeotrope. As shown in Table 1 below, the boiling pointof this composition fluctuates only about 0.7° C. as the HFC134a:HFC-365mfc mixture changes from a weight ratio of 100:0 to a weightratio of 65:35. TABLE 1 HFC134a: HFC365mfc Composition at 14.4 psia Δfrom 100% HFC Wt. % HFC 365 mfc Wt. % HFC 134a T (° C.) 134a 0.00 100.00−25.6 — 0.66 99.34 −26.2 −0.5 3.85 96.15 −26.3 −0.7 6.83 93.17 −26.2−0.6 12.28 87.72 −26.1 −0.5 17.13 82.87 −25.9 −0.3 23.47 76.53 −25.8−0.2 28.92 71.08 −25.6 0.0 35.07 64.93 −25.1 0.5

Example 7

Approximately 19.86 grams of HFC-134a was added to the ebulliometerdescribed in Example 5. HCF-43-10 is added in small increments.Temperature depression was observed when the HCF-43-10 is added,indicating a minimum boiling azeotrope. As shown in Table 2 below, theboiling point of this composition fluctuates only about 0.7° C. as theHFC134a: HCF-43-10 mixture changes from a weight ratio of 100:0 to aweight ratio of 45:55. TABLE 2 HFC134a: HFC-43-10 Composition at 14.4psia T Wt. % HFC-43-10 Wt. % HFC 134a (° C.) Δ from 100% HFC 134a 0.00100.00 −25.2 — 0.80 99.20 −25.8 −0.6 3.12 96.88 −25.9 −0.7 5.34 94.66−25.9 −0.7 7.46 92.54 −25.9 −0.7 10.78 89.22 −25.8 −0.6 16.76 83.24−25.6 −0.4 22.00 78.00 −25.5 −0.3 26.61 73.39 −25.4 −0.2 30.70 69.30−25.4 −0.2 37.66 62.34 −25.2 0.0 43.35 56.65 −25.0 0.2 49.16 50.84 −25.00.2 53.88 46.12 −24.9 0.3

1. An azeotrope or azeotrope-like composition comprising1,1,1,2-tetrafluoroethane and one or more compounds selected from thegroup consisting of 1,1,1,3,3-pentafluoropropane,1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane.2. The azeotrope or azeotrope-like composition of claim 1, comprising1,1,1,2-tetrafluoroethane and two or more compounds selected from thegroup consisting of 1,1,1,3,3-pentafluoropropane,1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane.3. The composition of claim 1 comprising from about 1 to about 99 weightpercent 1,1,1,2-tetrafluoroethane and from about 99 to about 1 weightpercent 1,1,1,3,3-pentafluoropropane, wherein said composition has aboiling point of approximately −25° to −26° C. at 14.4 psia.
 4. Thecomposition of claim 1 comprising from about 1 to about 20 weightpercent 1,1,1,2-tetrafluoroethane and from about 99 to about 80 weightpercent 1,1,1,3,3-pentafluoropropane, wherein said composition has aboiling point of approximately −25° to −26° C. at 14.4 psia.
 5. Thecomposition of claim 1 comprising from about 1 to about 10 weightpercent 1,1,1,2-tetrafluoroethane and from about 99 to about 90 weightpercent 1,1,1,3,3-pentafluoropropane, wherein said composition has aboiling point of approximately −25° to −26° C. at 14.4 psia.
 6. Thecomposition of claim 1 comprising from about 1 to about 10 weightpercent 1,1,1,2-tetrafluoroethane and from about 99 to about 90 weightpercent 1,1,1,3,3-pentafluoropropane, wherein said composition has aboiling point of approximately −25° to −26° C. at 14.4 psia.
 7. Thecomposition of claim 2 consisting essentially of about 20 weight percent1,1,1,2-tetrafluoroethane, about 30 weight percent1,1,1,3,3-pentafluorobutane, and about 50 weight percent1,1,1,3,3-pentafluoropropane.
 8. An azeotrope-like compositionconsisting essentially of about 65 to 99 weight percent1,1,1,2-tetrafluoroethane and 1 to 40 weight percent1,1,1,3,3-pentafluorobutane, wherein said composition has a boilingpoint of approximately −25° to −26° C. at 14.4 psia.
 9. Anazeotrope-like composition consisting essentially of about 45 to 99weight percent 1,1,1,2-tetrafluoroethane and 1 to 55 weight percent1,1,1,2,2,3,4,5,5,5-decafluoropentane, wherein said composition has aboiling point from approximately −25° to −26° C. at 14.4 psia.
 10. Amethod of removing a contaminant from a vapor compression systemcomprising the steps of: a. providing a vapor compression system havingat least a portion of at least one surface soiled with a contaminant; b.contacting said soiled surface with an azeotrope or azeotrope-likecomposition according to claim 1; and c. removing at least a portion ofsaid azeotrope or azeotrope-like composition from said system.
 11. Themethod of claim 10, wherein said contaminant is selected from the groupconsisting of lubricants, processing fluids, and sludge.
 12. The methodof claim 11, wherein said contaminant consists essentially of carbon,hydrogen, and optionally, oxygen atoms.
 13. The method of claim 12,wherein said contaminant comprises alkylbenzenes, mineral oils, esters,polyalkyleneglycols, and polyvinylethers.
 14. The method of claim 10,wherein said contacting step comprises flushing said contaminatedsurface with said azeotrope or azeotrope-like composition.
 15. Themethod of claim 14, wherein said flushing comprises the use of aflushing apparatus.
 16. The method of claim 15 wherein said flushingapparatus is a flush gun.
 17. A non-azeotrope composition comprising1,1,1,2-tetrafluoroethane and one or more compounds selected from thegroup consisting of 1,1,1,3,3-pentafluoropropane,1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane.18. The non-azeotrope composition of claim 17, comprising1,1,1,2-tetrafluoroethane and two or more compounds selected from thegroup consisting of 1,1,1,3,3-pentafluoropropane,1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane.19. A method of removing a contaminant from a surface comprising: (a)contacting the surface with an azeotrope or azeotrope-like compositioncomprising 1,1,1,2-tetrafluoroethane and one or more compounds selectedfrom the group consisting of 1,1,1,3,3-pentafluoropropane,1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane;and (b) removing at least a portion of said azeotrope or azeotrope-likecomposition from said surface.
 20. A method of removing a contaminantfrom a surface comprising: (a) contacting the surface with anon-azeotrope composition comprising 1,1,1,2-tetrafluoroethane and oneor more compounds selected from the group consisting of1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and1,1,1,2,2,3,4,5,5,5-decafluoropentane; and (b) removing at least aportion of said non-azeotrope composition from said surface.